Staff directory
Gustavo Ceballos Mago
Head of Research Support Division - Instrumentation Unit
gustavo.ceballos(ELIMINAR)@icn2.cat
Research Support Division - Instrumentation Unit
- ORCID: 0000-0002-6713-7963
Publications
2020
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Stabilizing Edge Fluorination in Graphene Nanoribbons
Panighel M., Quiroga S., Brandimarte P., Moreno C., Garcia-Lekue A., Vilas-Varela M., Rey D., Sauthier G., Ceballos G., Peña D., Mugarza A. ACS Nano; 14 (9): 11120 - 11129. 2020. 10.1021/acsnano.0c01837. IF: 14.588
The on-surface synthesis of edge-functionalized graphene nanoribbons (GNRs) is challenged by the stability of the functional groups throughout the thermal reaction steps of the synthetic pathway. Edge fluorination is a particularly critical case in which the interaction with the catalytic substrate and intermediate products can induce the complete cleavage of the otherwise strong C-F bonds before the formation of the GNR. Here, we demonstrate how a rational design of the precursor can stabilize the functional group, enabling the synthesis of edge-fluorinated GNRs. The survival of the functionalization is demonstrated by tracking the structural and chemical transformations occurring at each reaction step with complementary X-ray photoelectron spectroscopy and scanning tunneling microscopy measurements. In contrast to previous attempts, we find that the C-F bond survives the cyclodehydrogenation of the intermediate polymers, leaving a thermal window where GNRs withhold more than 80% of the fluorine atoms. We attribute this enhanced stability of the C-F bond to the particular structure of our precursor, which prevents the cleavage of the C-F bond by avoiding interaction with the residual hydrogen originated in the cyclodehydrogenation. This structural protection of the linking bond could be implemented in the synthesis of other sp2-functionalized GNRs. © 2020 American Chemical Society.
2019
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Critical Role of Phenyl Substitution and Catalytic Substrate in the Surface-Assisted Polymerization of Dibromobianthracene Derivatives
Moreno C., Panighel M., Vilas-Varela M., Sauthier G., Tenorio M., Ceballos G., Peña D., Mugarza A. Chemistry of Materials; 31 (2): 331 - 341. 2019. 10.1021/acs.chemmater.8b03094. IF: 10.159
Understanding the nature and hierarchy of on-surface reactions is a major challenge for designing coordination and covalent nanostructures by means of multistep synthetic routes. In particular, intermediates and final products are hard to predict since the reaction paths and their activation windows depend on the choice of both the molecular precursor design and the substrate. Here, we report a systematic study of the effect of the catalytic metal surface to reveal how a single precursor can give rise to very distinct polymers that range from coordination and covalent nonplanar polymer chains of distinct chirality to atomically precise graphene nanoribbons and nanoporous graphene. Our precursor consists on adding two phenyl substituents to 10,10′-dibromo-9,9′-bianthracene, a well-studied precursor in the on-surface synthesis of graphene nanoribbons. The critical role of the monomer design in the reaction paths is inferred from the fact that the phenyl substitution leads to very distinct products in each one of the studied metallic substrates. © 2018 American Chemical Society.
2018
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Bottom-up synthesis of multifunctional nanoporous graphene
Moreno C., Vilas-Varela M., Kretz B., Garcia-Lekue A., Costache M.V., Paradinas M., Panighel M., Ceballos G., Valenzuela S.O., Peña D., Mugarza A. Science; 360 (6385): 199 - 203. 2018. 10.1126/science.aar2009. IF: 41.058
Nanosize pores can turn semimetallic graphene into a semiconductor and, from being impermeable, into the most efficient molecular-sieve membrane. However, scaling the pores down to the nanometer, while fulfilling the tight structural constraints imposed by applications, represents an enormous challenge for present top-down strategies. Here we report a bottom-up method to synthesize nanoporous graphene comprising an ordered array of pores separated by ribbons, which can be tuned down to the 1-nanometer range. The size, density, morphology, and chemical composition of the pores are defined with atomic precision by the design of the molecular precursors. Our electronic characterization further reveals a highly anisotropic electronic structure, where orthogonal one-dimensional electronic bands with an energy gap of ∼1 electron volt coexist with confined pore states, making the nanoporous graphene a highly versatile semiconductor for simultaneous sieving and electrical sensing of molecular species. 2017 © The Authors
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On-surface synthesis of superlattice arrays of ultra-long graphene nanoribbons
Moreno C., Paradinas M., Vilas-Varela M., Panighel M., Ceballos G., Peña D., Mugarza A. Chemical Communications; 54 (68): 9402 - 9405. 2018. 10.1039/c8cc04830d. IF: 6.290
We report the on-surface synthesis of graphene nanoribbon superlattice arrays directed by the herringbone reconstruction of the Au(111) surface. The uniaxial anisotropy of the zigzag pattern of the reconstruction defines a one dimensional grid for directing the Ullmann polymerization and inducing periodic arrays of parallel ultra-long nanoribbons (>100 nm), where the periodicity is varied with coverage at discrete values following a hierarchical templating behavior. © 2018 The Royal Society of Chemistry.
2017
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Inorganic Photocatalytic Enhancement: Activated RhB Photodegradation by Surface Modification of SnO2 Nanocrystals with V2O5-like species (vol 7, 44763, 2017)
Epifani, Mauro; Kaciulis, Saulius; Mezzi, Alessio; Altamura, Davide; Giannini, Cinzia; Diaz, Raul; Force, Carmen; Genc, Aziz; Arbiol, Jordi; Siciliano, Pietro; Comini, Elisabetta; Concina, Isabella Scientific Reports; 7 2017. 10.1038/srep46855. IF: 4.259
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Symmetry forbidden morphologies and domain boundaries in nanoscale graphene islands
Parreiras S.O., Gastaldo M., Moreno C., Martins M.D., Garcia-Lekue A., Ceballos G., Paniago R., Mugarza A. 2D Materials; 4 (2, 025104) 2017. 10.1088/2053-1583/aa70fa. IF: 6.937
The synthesis of graphene nanoislands with tailored quantum properties requires an atomic control of the morphology and crystal structure. As one reduces their size down to the nanometer scale, domain boundary and edge energetics, as well as nucleation and growth mechanisms impose different stability and kinetic landscape from that at the microscale. This offers the possibility to synthesize structures that are exclusive to the nanoscale, but also calls for fundamental growth studies in order to control them. By employing high-resolution scanning tunneling microscopy we elucidate the atomic stacking configurations, domain boundaries, and edge structure of graphene nanoislands grown on Ni(1 1 1) by CVD and post-annealed at different temperatures. We find a non-conventional multistep mechanism that separates the thermal regimes for growth, edge reconstruction, and final stacking configuration, leading to nanoisland morphologies that are incompatible with their stacking symmetry. Whole islands shift their stacking configuration during cooling down, and others present continuous transitions at the edges. A statistical analysis of the domain structures obtained at different annealing temperatures reveals how polycrystalline, ill-defined structures heal into shape-selected islands of a single predominant stacking. The high crystallinity and the control on morphology and edge structure makes these graphene nanoislands ideal for their application in optoelectronics and spintronics. © 2017 IOP Publishing Ltd.
2015
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Substrate-induced stabilization and reconstruction of zigzag edges in graphene nanoislands on Ni(111)
Garcia-Lekue A., Olle M., Sanchez-Portal D., Palacios J.J., Mugarza A., Ceballos G., Gambardella P. Journal of Physical Chemistry C; 119 (8): 4072 - 4078. 2015. 10.1021/jp511069y. IF: 4.772
We combine experimental observations by scanning tunneling microscopy (STM) and density functional theory (DFT) to reveal the most stable edge structures of graphene on Ni(111) as well as the role of stacking-driven activation and suppression of edge reconstruction. Depending on the position of the outermost carbon atoms relative to hollow and on-top Ni sites, zigzag edges have very different energies. Triangular graphene nanoislands are exclusively bound by the more stable zigzag hollow edges. In hexagonal nanoislands, which are constrained by geometry to alternate zigzag hollow and zigzag top edges along their perimeter, only the hollow edge is stable, whereas the top edges spontaneously reconstruct into the (57) pentagon-heptagon structure. Atomically resolved STM images are consistent with either top-fcc or top-hcp epitaxial stacking of graphene and Ni sites, with the former being favored by DFT. Finally, we find that there is a one-to-one relationship between the edge type, graphene stacking, and orientation of the graphene islands. © 2015 American Chemical Society.
2014
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Atomic monolayer deposition on the surface of nanotube mechanical resonators
Tavernarakis, A.; Chaste, J.; Eichler, A.; Ceballos, G.; Gordillo, M.C.; Boronat, J.; Bachtold, A. Physical Review Letters; 2014. 10.1103/PhysRevLett.112.196103. IF: 7.728
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Spin tuning of electron-doped metal-phthalocyanine layers
Stepanow, S.; Lodi Rizzini, A.; Krull, C.; Kavich, J.; Cezar, J.C.; Yakhou-Harris, F.; Sheverdyaeva, P.M.; Moras, P.; Carbone, C.; Ceballos, G.; Mugarza, A.; Gambardella, P. Journal of the American Chemical Society; 136 (14): 5451 - 5459. 2014. 10.1021/ja501204q. IF: 11.444
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Spin-dependent electron scattering at graphene edges on Ni(111)
Garcia-Lekue, A.; Balashov, T.; Olle, M.; Ceballos, G.; Arnau, A.; Gambardella, P.; Sanchez-Portal, D.; Mugarza, A. Physical Review Letters; 2014. 10.1103/PhysRevLett.112.066802. IF: 7.728
2012
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A nanomechanical mass sensor with yoctogram resolution
Chastem J. ; Eichler, A.; Moser, J.; Ceballos, G.; Rurali, R.; Bachtold, A. Nature Nanotechnology; 7: 301 - 304. 2012. .
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Yield and Shape Selection of Graphene Nanoislands Grown on Ni(111)
Olle, M. ; Ceballos, G.; Serrate, D.; Gambardella, P. Nano Letters; 12(9): 4431 - 4436. 2012. DOI: 10.1021/nl300897m.
2011
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Localization, splitting, and mixing of field emission resonances induced by alkali metal clusters on Cu(100)
Stepanow, S.; Mugarza, A.; Ceballos, G.; Gambardella, P.; Aldazabal, I.; Borisov, A.G.; Arnau, A. Physical Review B - Condensed Matter and Materials Physics; 83 2011. 10.1103/PhysRevB.83.115101.
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Mixed-valence behavior and strong correlation effects of metal phthalocyanines adsorbed on metals
Stepanow, S.; Miedema, P. S.; Mugarza, A.; Ceballos, G. ; Moras, P. ; Cezar, J. C.; Carbone, C. ; de Groot, F. M. F.; Gambardella, P. Physical Review B; 2011. .
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Spin coupling and relaxation inside molecule-metal contacts.
Mugarza, A.; Krull, C.; Robles, R.; Stepanow, S.; Ceballos, G.; Gambardella, P. Nature Communications; 2 2011. 10.1038/ncomms1497.
2010
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Giant spin and orbital moment anisotropies of a Cu-phthalocyanine monolayer
Stepanow, S.; Mugarza, A.; Ceballos, G.; Moras, P.; Cezar, J.C.; Carbone, C.; Gambardella, P. Physical Review B - Condensed Matter and Materials Physics; 82 2010. 10.1103/PhysRevB.82.014405.
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Orbital specific chirality and homochiral self-assembly of achiral molecules induced by charge transfer and spontaneous symmetry breaking
Mugarza A., Lorente N., Ordejón P., Krull C., Stepanow S., Bocquet M.-L., Fraxedas J., Ceballos G., Gambardella P. Physical Review Letters; 105 (11, 115702) 2010. 10.1103/PhysRevLett.105.115702.
We study the electronic mechanisms underlying the induction and propagation of chirality in achiral molecules deposited on surfaces. Combined scanning tunneling microscopy and ab initio electronic structure calculations of Cu-phthalocyanines adsorbed on Ag(100) reveal the formation of chiral molecular orbitals in structurally undistorted molecules. This effect shows that chirality can be manifest exclusively at the electronic level due to asymmetric charge transfer between molecules and substrate. Single molecule chirality correlates with attractive van der Waals interactions, leading to the propagation of chirality at the supramolecular level. Ostwald ripening provides an efficient pathway for complete symmetry breaking and self-assembly of homochiral supramolecular layers. © 2010 The American Physical Society.
2007
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Insulating ground state of Sn/Si(111)-(¿30 x¿30)R30°
S. Modesti; L. Petaccia; G. Ceballos; I. Vobornik; G. Panaccione; G. Rossi; L. Ottaviano; R. Larciprete; S. Lizzit; A. Goldoni Physical Review Letters; 2007. .
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Role of the electric field in surface electron dynamics above the vacuum level
J. I. Pascual; C. Corriol; G. Ceballos; I. Aldazabal; H.-P. Rust; K. Horn; J. M. Pitarke; P. M. Echenique; A. Arnau Physical Review B; 2007. .